G6PD deficiency (Glucose-6-phosphate dehydrogenase)

What is G6PD?

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common genetically inherited enzyme deficiency in humans, affecting 400 million people worldwide. It has a high prevalence in persons of African, Asian, and Mediterranean descent. It is inherited as an X-linked recessive disorder thus males having g6pd is more common.

G6PD is an important enzyme, or protein, that regulates various biochemical reactions in the body.It is responsible for keeping red blood cells healthy so they can function properly and live a normal life span. When a person is deficient in G6Pd, the red blood cells break down prematurely and this lead to early destruction of red blood cells which is known as hemolysis and it can eventually cause hemolytic anemia.

​Most persons with G6PD deficiency do not have symptoms. Symptomatic patients can present with neonatal jaundice and acute hemolytic anemia. Kernicterus is a rare complication of neonatal jaundice but can occur in certain populations, this can be fatal.

What causes G6Pd?

G6PD deficiency is an X-linked recessive genetic disorder with an inheritance pattern similar to that of hemophilia and color blindness. It is passed along from one or both parents to their child. The defective gene is located on the X chromosome, which is one of the two sex chromosomes in human. Men have only one X chromosome whereas women have two X chromosomes. In males, one altered copy of the gene is enough to cause G6PD deficiency. In females, however, a mutation would have to occur in both copies of the gene to cause G6PD deficiency. Since it is unlikely for females to have two altered copies of this gene, males tend to manifest the abnormality whereas females are most of the time carriers. Being a carrier, the female can pass the gene onto her children but she does not have any symptoms herself.

Clinical presentation of G6Pd deficiency

Most people do not have symptoms. Should hemolytic anemia occur, symptoms may occur. Hemolytic anemia happens when red blood cells are destroyed faster than the body can produce them, resulting in reduced oxygen flow to the organs and tissues.

Symptoms of G6PD deficiency can include:

Neonatal jaundice: It usually appears within 24 hours after birth. Exchange transfusions are often required.

Tachycardia: rapid heart rate

shortness of breath

urine that is dark or yellow-orange

fever

fatigue

reduced effort tolerance

dizziness

confusion

paleness : due to break down of red blood cells

jaundice: yellowing of the skin and whites of the eyes

enlarged spleen and liver

heart murmur

What causes Hemolytic Anemia?​In people with G6PD deficiency, hemolytic anemia causes break down of red blood cells and reduced oxygen to tissues and organs (oxidative stress). Hemolysis begins 24 to 72 hours after exposure to oxidant stress. It can occur after eating certain foods and it can also be triggered by infections and certain drugs:

Peripheral blood smear: Heinz bodies (denatured hemoglobin) can be seen

Ultrasound abdomen: enlarged spleen and gallstones are common in patients with G6PD deficiency

Treatment of G6PD

Most people with glucose-6-phosphate dehydrogenase (G6PD) deficiency do not need treatment. However, they should be taught to avoid drugs and food like fave beans that can cause oxidant stress. Identification and discontinuation of the precipitating agent is critical to manage hemolysis. Acute hemolysis is self limiting and will resolve in 8-14 days. Transfusions are rarely necessary and removal of spleen is usually ineffective.

In neonates with prolonged jaundice due to G6PD deficiency should receive phototherapy with a bili light. Exchange transfusion may be carried out in those with severe neonatal jaundice or hemolytic anemia caused by favism (fava beans).​Patients with chronic hemolysis or non-spherocytic anemia should be placed on daily folic acid supplements.